SCHOTT solutions no. 2/2009 > Astronomy

X-ray light cannot be focused to form a sharp image using normal lenses. The refractive index of this part of the electromagnetic spectrum is nearly the same for the vacuum. X-rays can be bundled using conically tapered cylinder mirrors with a high density metal coating on a super-smooth substrate. This is why the Japanese astronomers are using the Duran® glass that Otto Schott invented at the end of the 19th century as their model. With roughness of only a few atomic diameters in height, the surface of this glass is almost perfectly smooth. Japanese technicians vapor deposit various metal coatings onto it, bond them together and remove them from the glass once again to obtain their glossy mirrors. “We tested glass tubes from several manufacturers, but the best ones came from SCHOTT!” Kunieda says. And he certainly knows what he is talking about: the Japanese space agency already used special glasses from SCHOTT for the space telescope Suzaku, the predecessor to Astro-H.

If it would be possible for us humans to see x-rays, we would be looking into the evening sky with completely different eyes. We could see through galactic fog or clouds of dust just as doctors are able to view our bones through tissue made of flesh and skin. And like doctors, astronomers are using x-ray satellites to expand their view from the surface to the depths. Nevertheless, they are not interested in learning more about how healthy the universe is – at least there are no signs of any real deficiencies. More importantly, these sky scouts are hoping to learn more about exotic objects like black holes, galactic particle accelerators and the dynamics of hot plasma from which the planets or stars perhaps originate. “We thus learn more about the history of our origins and probably even our fate,” Kunieda explains.

These types of observations cannot be made from here on Earth. Our atmosphere does not allow this part of the electromagnetic spectrum to pass through. And luckily so! After all, life never would have been able to develop while our planet was being bombarded with hard x-rays that also lash down on us from the sun. With a weight of 2.4 tons and a length of 14 meters, Astro-H (here the “H” indicates that it is the eighth astronomy satellite) ranks as the largest and heaviest satellite that the cosmologists from the “Land of the Rising Sun” have ever sent into space. Astro-H, which its creators also affectionately call NeXT (for New X-ray Telescope), is a co-production of the American space agency NASA and Europe’s ESA under the leadership of the Japanese space agency JAXA. <|